Messages in this thread Patch in this message | | | Date | Mon, 23 Jan 2006 17:28:53 +0100 | From | Eric Dumazet <> | Subject | Re: [PATCH] garbage values in file /proc/net/sockstat |
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Andi Kleen a écrit : > On Monday 23 January 2006 14:28, Eric Dumazet wrote: > >> Shouldnt we force a page fault for not possible cpus in cpu_data >> to catch all access to per_cpu(some_object, some_not_possible_cpu) ? >> >> We can use a red zone big enough to hold the whole per_cpu data. > > Good idea. Can you please send me a tested patch? >
I did a patch (on top of 2.6.16-rc1-mm2) , but the kernel crashes in sched_init(void)
for (i = 0; i < NR_CPUS; i++) { prio_array_t *array; rq = cpu_rq(i); spin_lock_init(&rq->lock); <<-CRASH
In my config, NR_CPUS = 8, and I have one only one CPU inside my test box.
So should I send only the patch or all the corrections I have to do to avoid all possible crashes in my config ?
Thank you Eric Dumazet
[PATCH] x86_64 : Use a special CPUDATA_RED_ZONE to catch accesses to per_cpu(some_object, some_not_possible_cpu)
Because cpu_data(cpu)->data_offset may contain garbage, some buggy code may do random things without notice. If we initialize data_offset so that the per_cpu() data sits in an unmapped memory area, we should get page faults and stack traces should help us find the bugs.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
--- linux-2.6.16-rc1/Documentation/x86_64/mm.txt 2006-01-17 08:44:47.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/Documentation/x86_64/mm.txt 2006-01-23 16:54:46.000000000 +0100 @@ -5,7 +5,8 @@ 0000000000000000 - 00007fffffffffff (=47bits) user space, different per mm hole caused by [48:63] sign extension -ffff800000000000 - ffff80ffffffffff (=40bits) guard hole +ffff800000000000 - ffff807fffffffff (=39bits) guard hole +ffff808000000000 - ffff80ffffffffff (=39bits) not possible cpus percpudata hole ffff810000000000 - ffffc0ffffffffff (=46bits) direct mapping of all phys. memory ffffc10000000000 - ffffc1ffffffffff (=40bits) hole ffffc20000000000 - ffffe1ffffffffff (=45bits) vmalloc/ioremap space --- linux-2.6.16-rc1/include/asm-x86_64/pgtable.h 2006-01-17 08:44:47.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/include/asm-x86_64/pgtable.h 2006-01-23 16:54:46.000000000 +0100 @@ -136,6 +136,7 @@ #ifndef __ASSEMBLY__ #define MAXMEM 0x3fffffffffffUL +#define CPUDATA_RED_ZONE 0xffff808000000000UL #define VMALLOC_START 0xffffc20000000000UL #define VMALLOC_END 0xffffe1ffffffffffUL #define MODULES_VADDR 0xffffffff88000000UL --- linux-2.6.16-rc1/arch/x86_64/kernel/setup64.c 2006-01-23 16:36:38.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/arch/x86_64/kernel/setup64.c 2006-01-23 16:58:30.000000000 +0100 @@ -99,9 +99,13 @@ size = PERCPU_ENOUGH_ROOM; #endif - for_each_cpu_mask (i, cpu_possible_map) { + for (i = 0 ; i < NR_CPUS ; i++) { char *ptr; + cpu_pda(i)->data_offset = (char *)CPUDATA_RED_ZONE - __per_cpu_start; + if (!cpu_possible(i)) + continue; + if (!NODE_DATA(cpu_to_node(i))) { printk("cpu with no node %d, num_online_nodes %d\n", i, num_online_nodes()); | |